This invention relates to apparatus for supplying controlled amplitudes of direct current voltage or current from a line of alternating current voltage. Such a power supply is generally comprised of a power transformer for providing a desired amplitude of alternating current voltage, a rectifier for converting this alternating current voltage to a direct current voltage that is applied to a filter or storage capacitor, and a regulator for maintaining the output voltage or current at selected values. In order to dissipate the heat generated in the regulator, a heat sink is required.
A basic power supply such as this is capable of providing any voltage up to its rated maximum V.sub.r in combination with any current up to the rated maximum L.sub.r. The rated power output V.sub.r I.sub.r occurs only at one point V.sub.r, I.sub.r. In practice it is often required that a supply operate up to relatively large values of voltage and current. However, not all combinations of voltage and current up to V.sub.r and I.sub.r are generally required. It is more important to supply a large voltage at a low current and a large current at a low voltage. This means that the power output can be much less than V.sub.r I.sub.r.
Various power supplies have been built that selectively provide different combinations of maximum voltage V.sub.r and maximum current I.sub.r, in which the power output for each combination is less than the largest V.sub.r times the largest I.sub.r. Whereas some advantage in cost and size is thereby derived, separate filter capacitors and completely separate secondary windings of the power transformer are used so that bulk and cost are still a problem.